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The CDC also estimates that between 2.9 million and 3.5 million people have seen a doctor because of the flu since the season began in October. Between 69,300 and 83,500 people have been hospitalized because of the virus.

Thirty states have reported widespread flu activity, although flu is present in every state. Fifteen states reported high levels of flu activity as of the week ending January 5. That's four fewer states than the previous week.

The number of children who died of flu increased. Three children's deaths related to the flu were reported in the week ending January 5, bringing the pediatric death toll to 16 for this season, according to the CDC.

Provisional data on how well this season's flu vaccine is working to prevent people from getting sick won't be available for at least several more weeks, according to the CDC.

Instead of relying on people to get vaccinated every year, scientists are getting closer to a flu vaccine that would last through multiple seasons, called a universal flu vaccine.

"It will be a game-changer," said Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Disease at the National Institutes of Health. "It also would very likely be a much more effective vaccine than the ones we have to make each year, hoping that we guess accurately as to what the influenza virus that season will be."

The National Institutes of Health is investigating several methods to achieve a universal vaccine.